This invention relates to a scroll compressor having a controlled oil injection wherein the amount of oil injected between the scroll members is increased under certain operational conditions.
Scroll compressors are becoming widely utilized in refrigerant applications. In a scroll compressor, a first scroll member has a base and a generally spiral wrap extending from its base. The second scroll member has a base with a generally spiral wrap extending from its base. The wraps of the two scroll members interfit to define compression chambers. The second scroll member is caused to orbit relative to the first scroll member, and during this orbiting movement, the compression chambers decrease in volume, comprising an entrapped refrigerant.
The tips of the wraps of each of the scroll members are in contact with the base of the opposed scroll member during this movement. Further, there are other relatively moving surfaces on the scroll members. It is known to supply lubricant to the scroll members to lubricate the interface between the tips and the base, and other surfaces.
In one successful method, lubricant is driven into a suction chamber positioned radially outwardly of the scroll wraps, and is entrained in the refrigerant moving through the scroll compressor. The volume flow of refrigerant typically entrains a particular amount of lubricant. The amount of lubricant reaching the scroll member surfaces is typically dependent on the volume flow of refrigerant.
As an example, a typical lubricant flow of approximately 1% per volume of refrigerant is standard during normal operational conditions of a scroll compressor. Various ways have been developed to inject oil into the compression chambers, and the size of the flow passages, restrictions, etc. are selected to achieve an acceptable amount of lubricant during this normal operation.
Scroll compressors are subject to some operational challenges. As an example, if there is a lower than expected amount of refrigerant in the system, a so-called loss of charge situation, then the volume of refrigerant moving through the scroll compressor is less than expected or desired.
Other challenges relate to so-called xe2x80x9creverse runningxe2x80x9d condition. In one type of reverse running condition, the motor for the scroll compressor may be improperly wired if it is a three-phase powered motor. When this occurs, the second scroll member is caused to orbit in an opposed and undesired direction. Again, the volume of refrigerant flowing through the compressor will be much less than expected.
In such situations, the challenges on the relatively moving surfaces between the scroll member are even greater than normal. Temperatures are higher than would be expected, and providing an acceptable amount of lubricant becomes even more important. However, in a loss of charge situation, or reverse rotation, the volume flow is undesirably low and the percentage of lubricant entrained by the refrigerant will also be less than even normally supplied.
Thus, it would be desirable to develop a method of lubricating the sliding surfaces on the scroll members in such a fashion that additional lubricant is supplied under certain operational conditions.
In the disclosed embodiment of this invention, a condition responsive valve is positioned in a lubricant supply passage. The condition responsive valve is maintained in a first relatively closed position under normal operating conditions. However, should conditions in the compressor indicate an operational challenge, the valve can open, allowing increased flow of lubricant. In a disclosed embodiment, the valve is temperature responsive to move between two positions. In a most preferred embodiment, the valve is located to restrict, but allow flow through a lubricant supply passage under normal conditions. If the valve senses a temperature above a predetermined maximum, then the valve moves to a second position at which it is less restrictive to the flow of lubricant.
In preferred embodiments, the valve is positioned in the non-orbiting scroll, and includes a bi-metal element which snaps between two positions to allow the valve to move to the two positions, as described above. In further embodiments, a spring may bias the valve to its normal position, and the bi-metal snap element moves against the force of the spring to allow the valve to move to its less-restrictive position.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.